In the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities there have been, and continue to be, efforts toward scaling down device dimensions (e.g., at sub-micron levels) on semiconductor wafers. In order to accomplish such high device packing densities, smaller feature sizes and more precise feature shapes are required. This may include the width, thickness and spacing of interconnecting lines, spacing and diameter of contact holes, and the surface geometry, such as corners and edges, of various features.
The requirement of small features with close spacing between adjacent features requires sophisticated manufacturing techniques to ensure that quality and operability of the features are not compromised for the purpose of reducing feature size. Among the many aspects related to improving semiconductor fabrication processing to achieve higher density devices, the ability to deposit continuous, amorphous or crystalline thin films, which are substantially free from impurities and defects, remains critical to the structural integrity of smaller features as well as to the performance of the device with respect to increasing the speed of the device. Even minor impurities or defects present on the thin film layer tend to result in poor device characteristics, thereby reducing the effectiveness of the semiconductor device.
Several techniques for depositing thin films are known in the art. One exemplary technique for depositing a thin film is via chemical vapor deposition (CVD), wherein a wafer is introduced into a process chamber, heated to a desired temperature and gases are flown to initiate the deposition process. As in many conventional thin film deposition techniques, this CVD process inevitably permits the introduction of impurities into the deposited thin film layer. In CVD, a combination of inert carrier gasses and reactant gasses are introduced into the chamber wherein the elevated wafer temperature causes the reactive gasses to break down on the wafer surface thereby depositing the desired thin film on the wafer surface. To maintain the desired chemical reaction, the desired temperature in the chamber and at the wafer surface must be maintained. Accordingly, the wafer may be in continuous and direct contact with a means for heating the wafer. The means for heating the wafer (e.g. ceramic, quartz or metal susceptor) may release impurities into the deposition chamber, which may be deposited in the thin film layer. Conductive impurities can negatively impact the manufactured chip by, for example, producing electrical shorts, while non-conducting impurities can negatively impact the manufactured chip by, for example, increasing the resistance of conductive layers.
Another method for depositing thin films is via plasma enhanced chemical vapor deposition (PECVD). When PECVD is used to produce thin films, vapors including elements such as fluorine and carbon may be employed in cleaning the deposition chamber wherein the PECVD occurs. Remnants of the fluorine and carbon may remain in the deposition chamber after cleaning and thus may be incorporated into a thin film layer in subsequent deposition processes. Such impurities can negatively impact the quality of the manufactured chip by altering the desired electrical properties of and interactions between components on the manufactured chip. Novel deposition techniques are used for new materials employed in the semiconductor industry. For example, in deposition techniques such as MOCVD (Metal Organic Chemical Vapor Deposition), PLD (Pulsed Laser Deposition), ALCVD (Atomic Layer Chemical Vapor Deposition) and LPCVD (Low Pressure Chemical Vapor Deposition), which use liquid or solid precursors, the remnants of carbon or other unreacted organic or metal particles can be incorporated in the films, leading to failure of the device.
Thus, an efficient system and/or method to control thin film deposition and monitor defects and impurities in thin films are desired to increase quality and reliability in IC manufacture.